We have established that adenylate cyclase in broken cell preparations shows no regulation by effectors; however, in intact cells, glucose effectively inhibits adenylate cyclase. Sugar other than glucose will inhibit adenylate cyclase provided their transport systems are present. Our currently available data suggest that the membrane- bound adenylate cyclase of E. coli represents a powerful model system for the regulation by effectors of adenylate cyclase. Further studies in this system may provide insight into the mechanism by which receptor- bound hormones influence adenylate cyclase.